"They are sooooo cool." Well, so what makes them cool? Is it the handbag they carry or the CDs they listen to, or the paintings they collect or the books they read? Perhaps it's all of the above, according to Nancy MacDonell, author of a new book, "In the Know: The Classic Guide to Being Cultured and Cool." (Penguin Books).

COOL COAT - Accessories may be the ultimate sign of a cool fashionista, but a wonderful coat is also a symbol of put-together style. CNS Photo courtesy of Anthropologie.

"Cool is maddeningly elusive to define, which is part of its allure," says MacDonell, an editor at www.style.com who lives in New York and has written for loads of fashion magazines.

"In the Know" is a one-volume, pocket-sized guidebook, and is MacDonell's personal interpretation on everything from five cocktails to order to five artists to watch to five cities to visit now to five fashion pieces to spend your money on.

It's a great read and a good reference to all that's hip. And a perfect Christmas gift - tied up with Billie Holiday's "Lady in Satin" CD - a must for every "cool" music collector.

So what does MacDonell suggest you cool fashionistas spend your money on? Accessories, of course.

"Clothes are generic," she says. "It's the details that set you apart - and add a good coat!"

Number one on the cool hunter's list is a handbag.

"Fashion people select their bags on the premise that even if they were to run out of their apartments naked during a fire, with no time to grab anything else, they would still be identifiable as fabulous," says MacDonell.

Now, you can overdo this one, especially if your logos are showing, she adds. So even if the "It" bags change from year to year, here are a few of the "cool" ones you can always rely on: the Hermes Birkin or Kelly, a classic quilted Chanel bag with a chain handle, or a woven Bottega Veneta tote.

"Once you've acquired a suitably impressive bag," says MacDonell, "carry it casually, as though you think nothing of swinging several thousand dollars' worth of leather from your wrist."

Shoes are also at the top of the style.com editor's list of accessories to spend money on.

"Shoes are a fashionista's flirty Ginger Rogers to the more polished Fred Astaire appeal of a handbag," she says. "To paraphrase Katharine Hepburn's quip about the dancing duo, a bag gives you class, shoes give you sex," adds MacDonell.

And yes, you can go overboard on this fashionable necessity, too. You can't be cool when you're tripping over your sky-high heels and falling flat on your face.

And when it comes to cool jewelry, there's a trick, according to MacDonell. "Avoid the mundane. Think outside the Tiffany blue box."

Perhaps something a little different than your standard strand of pearls.

"Vintage jewels are always good," says the "In the Know" author, "especially if they have unusual settings - art deco, Victorian - and an interesting story behind them."

Sunglasses are often the epitome of cool glamour and status.

"Because pretty much anyone looks more impressive in sunglasses," says MacDonell. "And people will always spend money to look more impressive."

Big is better when it comes to stylish sunglasses, she notes. But when they get too big, "ridiculously oversize is merely ridiculous."

And the one piece of clothing you should spend big bucks on is a coat, of course.

"A well-made coat makes you feel instantly pulled together," states MacDonell. "It also sees a lot of wear and gets far more display time than what goes beneath it; all good reasons to look on it as an investment."

Sharon Mosley is a former fashion editor of the Arkansas Gazette in Little Rock and executive director of the Fashion Editors and Reporters Association.